Background and Significance. In 2003-2005 Group Health implemented pharmacy-based, system- wide outreach efforts that increased statin use in enrollees with diabetes from about 30 to 70%. Few studies have examined whether a large, population-level increase in statin use benefits macrovascular disease progression in adults with diabetes, and whether the benefits are similar for patients with different comorbid conditions. The issue is significant for comparative effectiveness research (CER) because most deaths among patients with diabetes are for cardiovascular disease, and reducing macrovascular disease progression through statin and ACE (angiotensin-converting enzyme) inhibitor treatments is an important element of diabetes care. Aims. For the population of adult enrollees with diabetes mellitus continuously enrolled in Group Health in 1997-2010, aims are to: 1) Describe the utilization of HMG-CoA reductase inhibitors (statins) and ACE inhibitors by comorbid group in 1998-2010;and 2) Following Group Health outreach, estimate the associations between statin and ACE inhibitor use and major vascular events and clinical quality of care in 2006-2010 by comorbid group. Population. 6,856 Group Health adult enrollees in Group Health Diabetes Registry with type 1 or 2 diabetes who were enrolled continuously from 1997-2006, survived to 2006, and will be followed through 2010. Co-morbid conditions are hypertension, coronary artery disease, congestive heart failure, and depression. Study Design. Population-based, retrospective longitudinal cohort. Data Sources. Group Health automated data bases. Measures. All-cause mortality, cardiovascular mortality, non-fatal myocardial infarction, stroke, LDL- cholesterol, blood pressure, hemoglobin A1c (HbA1c), four co-morbid conditions, diabetes complications, Charlson co-morbidity index, drug adherence, diabetes treatment type, personal and plan characteristics, smoking, obesity (BMI), utilization of providers and Web-based health information. Analyses. For Aim 1, descriptive statistics and time series graphs will be produced to describe time of exposure to statins and ACE inhibitors for the 1998-2002 pre-outreach years, the 2003-2005 outreach years, and 2006-2010 post-outreach years. Bivariate statistical tests will be performed to determine whether enrollee personal and clinical characteristics are associated with exposure to statins and ACE inhibitors in the pre-outreach, outreach, and post-outreach years. In Aim 2, Cox proportional hazards and other regression models will estimate the associations between statin and ACE inhibitor use and major vascular events and clinical quality of care in 2006-2010 by co-morbid group. PUBLIC HEALTH RELEVANCE: In 2003-2005 Group Health implemented pharmacy-based, system-wide outreach efforts that increased statin use in enrollees with diabetes from about 30 to 70%. Few studies have examined whether a large, population-level increase in statin use has health benefits for adults with diabetes, and whether the benefits are similar for patients with different co-morbid conditions. The issue is significant for comparative effectiveness research (CER) because most deaths among patients with diabetes are for cardiovascular disease, and reducing macrovascular disease progression through statin and ACE inhibitor treatments is an important element of diabetes care.